The present invention relates to a groove ring for the deflection unit of a television set, which deflection unit consists of a toroidal coil surrounding a toroidal core, and which groove ring is provided with grooves formed by ridges at the outer circumferential surface of the ring and at one ring surface and serving to both receive and adjust the coil wires and guide the core while the toroidal coil is being wound thereon. FIG. 1 shows such a core with a toroidal coil. German Published Application No. 2,113,065 describes the winding of such toroidal coils with the aid of groove rings and discloses an apparatus therefor, which is shown in FIG. 2. The core is advanced during the winding operation by means of a gear which meshes with the grooves and turns the core forward and back as desired, with at least two contact rollers holding the ring in a freely rotatable position. Since, in such an arrangement, the ridges between the individual grooves have to be narrow so that the coil wires can be laid into the grooves, the applicant itself states in the above German Published Application that the grooves or the ridges forming the grooves are too weak for a gear drive, because the pressure forces are too high, so that the ridges will break out. To prevent this, German Published Application No. 2,325,002 teaches to set back every second group of grooves from the circumference of the ring at regular intervals in such a manner that the intermediate groups of grooves and ridges, which are not set back, form a gear rim suited for advancing the core during the winding operation. FIG. 3 shows such a groove ring with a driving pin wheel; it corresponds to FIG. 2 of the aforementioned German Published Application. Although such teeth of the gear ring no doubt result in a certain increase in strength, the possibility of the ridges breaking out cannot be excluded, particularly if relatively high windings speeds are used.